Add and use TV specific unused apps page summary

The original unused_apps_page_summary message was created for Android Mobile and contains "Notification is stopped to save battery" fragment which doesn't make sense in context of the TV.

Bug: 222468351
Test: m -j99 GooglePermissionController
Test: installmod GooglePermissionController
Test: adb shell device_config put app_hibernation app_hibernation_enabled true
Change-Id: Ica7d0d4c02c2923a867d9c864308162982bb927d